Two types of compounds are being developed for use in mercury poisoning: polymeric chelating agents and low molecular weight water soluble chelating agents. Of the polymeric chelating agents, the compound (-CH2CH2-N-)n CH2COOH, with n approximately 5,000, used as its calcium complex appears to be an ideal material (PEIA). It possesses considerable chemical stability, is prepared as an odorless, tasteless white powder and is capable of raising the LD50 of CH3HgCl in mice when the polymer is administered orally. The LD50 of the polymer itself is greater than 3 g/kg orally in mice. A large scale preparation of this is to be developed as well as a more complete evaluation of its action in mercury poisoning and its general pharmacological properties. Several new low molecular weight chelating agents with the basic structure -C(S)-C(S)- have been prepared and will also be tested for their interaction with mercury both in vivo and in vitro. Polymers have been prepared with different structures than PEIA and these will also be examined further.